This improves compression but only by a very small bit
possibly it could be improved by exactly calculating the number of bits that
would be needed
Signed-off-by: Michael Niedermayer <michae...@gmx.at>
---
libavcodec/lpc.c | 49 +++++++++++++++++++++++++++++++++++++++++++++++--
1 file changed, 47 insertions(+), 2 deletions(-)
diff --git a/libavcodec/lpc.c b/libavcodec/lpc.c
index deb02e7..930e526 100644
--- a/libavcodec/lpc.c
+++ b/libavcodec/lpc.c
@@ -135,6 +135,51 @@ static void quantize_lpc_coefs(double *lpc_in, int order,
int precision,
*shift = sh;
}
+static void quantize_lpc_coefs2(double *lpc_in, int order, int precision,
+ int32_t *lpc_out, int *shift, int max_shift,
+ int zero_shift, const int32_t *samples, int len)
+{
+ int allsteps = 1;
+ int i, j, step, improved;
+ int64_t best_score = INT64_MAX;
+ int32_t qmax;
+
+ qmax = (1 << (precision - 1)) - 1;
+
+ quantize_lpc_coefs(lpc_in, order, precision, lpc_out, shift, max_shift,
zero_shift);
+
+ for (i=0; i<order; i++)
+ allsteps *= 3;
+
+ do {
+ improved = 0;
+ for (step = 0; step < allsteps; step++) {
+ int tmp = step;
+ int32_t lpc_try[MAX_LPC_ORDER];
+ int64_t score = 0;
+ for (i=0; i<order; i++) {
+ lpc_try[i] = av_clip(lpc_out[i] + ((tmp + 1) % 3) - 1, -qmax,
qmax);
+ tmp /= 3;
+ }
+ for (j=order; j<len; j++) {
+ int64_t v = 0;
+ for (i=0; i<order; i++) {
+ v += samples[j - 1 - i] * (int64_t)lpc_try[i];
+ }
+ v >>= *shift;
+ v -= samples[j];
+ score += FFABS(v);
+ }
+ if (score < best_score) {
+ best_score = score;
+ memcpy(lpc_out, lpc_try, sizeof(*lpc_out) * order);
+// improved=1;
+ }
+// av_log(0,0, "score %Ld\n", best_score);
+ }
+ } while(improved);
+}
+
static int estimate_best_order(double *ref, int min_order, int max_order)
{
int i, est;
@@ -255,10 +300,10 @@ int ff_lpc_calc_coefs(LPCContext *s,
if(omethod == ORDER_METHOD_EST) {
opt_order = estimate_best_order(ref, min_order, max_order);
i = opt_order-1;
- quantize_lpc_coefs(lpc[i], i+1, precision, coefs[i], &shift[i],
max_shift, zero_shift);
+ quantize_lpc_coefs2(lpc[i], i+1, precision, coefs[i], &shift[i],
max_shift, zero_shift, samples, blocksize);
} else {
for(i=min_order-1; i<max_order; i++) {
- quantize_lpc_coefs(lpc[i], i+1, precision, coefs[i], &shift[i],
max_shift, zero_shift);
+ quantize_lpc_coefs2(lpc[i], i+1, precision, coefs[i], &shift[i],
max_shift, zero_shift, samples, blocksize);
}
}
--
1.7.9.5
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